| 摘要: | CHINESE ABSTRACT
表面增強拉曼散射 (Surface-enhanced Raman scattering, SERS) 非常靈敏，是極具
應用價值的檢測工具。然而，過去 30 多年以來，SERS 的臨床應用一直受限於其有限
的再現性。本研究提出一種新型 SERS 感測器，利用氮化銦鎵量子井 (quantum wells,
QW) 改善 SERS 在空間上和時間上的再現性，也提升訊號強度。
為了釐清 QW 在 SERS 中的作用，我們以 R6G (rhodamine 6G) 分子研究不同 QW
結構的 SERS 光譜，並發現 QW 提供高濃度表面電荷能以兩種方式提高 SERS 的效能：
i)增強共振強度; ii)擴大 SERS 熱點 (hot spots)，進而形成熱面 (hot surface)。這些結果源
自於電荷轉移共振(charge-transfer resonance)和局域表面電漿共振(localized surface
plasmon resonance, LSPR)的增強。透過改變 QW 數量和表面形態，我們發現 SERS 的增
強因子(enhancement factor)與表面電子濃度呈現線性相關。此外，QW 裡的電子，能與
金奈米顆粒表面的電子共振，大幅增加熱點面積，產生大範圍的單分子訊號。
InGaN QWs 基板的獨特 SERS 性能被應用於循環腫瘤 DNA（circulating tumor
DNA, ctDNA）和葡萄糖的檢測。具體來說，透過結合鋁奈米結構和 QW，我們展現胰
臟癌 ctDNA 檢測的高靈敏、高特異和高穩定性。在葡萄糖方面，我們在複雜的細胞培
養液裡，觀察到不同濃度的葡萄糖（1-87 mM）訊號，驗證了 SERS 優越的特異性。此
外，我們更透過優化 InGaN QW 的能帶結構，觀察到胰臟癌和甲狀腺癌 ctDNA的 SERS
光譜差異。
我們相信，優化 QW的表面形態、厚度、摻雜濃度等參數，能持續推進 SERS 的
檢測效能，有助實現 SERS 的臨床應用。;ENGLISH ABSTRACT
Surface-enhanced Raman scattering (SERS) is a sensitive analysis tool for molecular
detection across various research fields. Nonetheless, the practical applications of SERS have
been impeded by its limited reproducibility for 30+ years. This work presents a novel SERS
sensor built with indium gallium nitride quantum wells (InGaN QWs), exhibiting greatly
improved reproducibility in space and time. Not only showing improved reproducibility, the
nitride QWs also deliver enhanced SERS intensity.
The roles of QW in SERS were investigated by detecting rhodamine 6G molecules on
the substrates with varied QW structures. It was found that the QWs improve SERS
performances via two routes: i) amplifying the SERS intensities and ii) forming the hot surface
by enlarging and interconnecting SERS-active regions. The two routes result from enhanced
effects of charge transfer resonance and localized surface plasmon resonance. Effective control
over electron distribution by QW number and surface morphology leads to a linear dependence
of SERS enhancement factor on surface electron concentration. In addition, QWs-induced
electrons were shown to coherently oscillate with those on gold nanoparticles, greatly enlarging
the hotspots and thus delivering the prevalent single-molecule signals.
The superior performance of InGaN QWs-based SERS substrates were applied to the
detection of circulating tumor deoxyribonucleic acid (ctDNA) and glucose. Specifically, by
combining aluminum nanostructures and QWs, we successfully achieved a sensitive (i.e.,
concentration of 10-13M), specific (single-base mismatch discrimination), and stable sensing of
ctDNA for pancreatic cancer diagnosis. Moreover, overcoming the challenges of low Raman
cross-section and complex environmental interference, we achieved an unprecedented detection
of glucose (1-87 mM) in culture cell medium, which was realized on gold nanostructures with
the QW-based hot surface. Furthermore, band-gap engineering of InGaN QWs led to enhanced
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SERS specificity, delivering distinct SERS signals of the two single-stranded ctDNA (10-5 M)
related to pancreatic and thyroid cancers.
These promising results can be further improved by optimizing the QW structures,
including surface morphology, well/barrier thickness, and doping concentration, paving the
way for practical applications of SERS biosensors. |
